<!DOCTYPE html>
<html lang="zh-CN">

<head>
  <meta charset="UTF-8">
  <meta name="viewport" content="width=device-width, initial-scale=1.0">
  <title>Document</title>
  <style>
    p {
      color: red;
    }

    p {
      /* 层叠覆盖：选择器优先级相同时，后设置的属性生效 */
      color: orange;
      /* 层叠叠加 */
      font-size: 16px;
    }
  </style>
</head>

<body>
  <p>Hello world!</p>
</body>

</html>